Opera before 10.00 does not check all intermediate X.509 certificates for revocation, which makes it easier for remote SSL servers to bypass validation of the certificate chain via a revoked certificate.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6357
https://euvd.enisa.europa.eu/vulnerability/EUVD-2009-3030
http://www.opera.com/support/kb/view/929/
http://www.opera.com/docs/changelogs/windows/1000/
http://www.opera.com/docs/changelogs/solaris/1000/
http://www.opera.com/docs/changelogs/mac/1000/